Process for the reactivation of clay



Patented June 13, 1939 PROCESS FOR THE REACTIVATION F CLAY George Hugovon Fuchs, Wood Riv'er, Ill., assignor to Shell Development Company, SanFrancisco, Calif., a corporation of Delaware No Drawing. Application May22, 1937,

Serial No.

c Claims. (Cl. 252-2) Such matter is held so tenaciously by the activesurface of the clay, that upon extraction with a suitable tar solvent itis ,10 dissolved very incompletely, and in order to regenerate the clam,substantially complete removal of adsorbed matter is necessary. To makeit available for dissolution, it must first be displaced from thesurface by a suitable displacing 15 agent, which has a. greater afiinityto the clay than the adsorbed matter.

Displacing agents are roughly of two classes,

depending upon whether their aflinity to the,

adsorbent is predominantly of chemical or physi- 20 cal nature. Alkalinesubstances, as alkali hydroxides, ammonia, etc., are examples ofchemical displacing agents for acidic adsorbents, salts of the acidiccomponents of the adsorbent being formed; while as against the sameadsorbents, 25 water, various types of acids, polar organic substances,etc., may be classified as physical displacing agents.

Whereas the chemical displacing agents are in general very powerful,they have the disad- =0 vantage that they usually require a subsequentchemical treatment for their .removalfrom the clay. 'Ifhus alkali usedto reactivate acidic clays must be removed by an acid treatment.Physically acting displacing agents on the other hand,

5 although in general not as powerful, are removed more easily, and ifsufficiently volatile, can be' expelled by simple heating.

Of the physical displacing agents, water has been recognized to possesshighest physical af- D flnity towardsclays.

lack of solvent power for organic mattersuch as tar, is incapable ofpenetrating the layer of adsorbed matter, and therefore cannot reach theactive surface of the clay. Thus in spite of its i highphysicalafiinity, water has in effect proven to be a very poordisplacing agent;

It is a purpose of this invention to'provide a simple method whichenables the use of water free of active acidic or basic chemicals, foref- 'fectively displacing adsorbedmatter from spent Water, however, dueto itsclay, thereby reactivating at least a portion of the clay; and itis another purpose to provide a process in which properly reactivatedportions of the clay can be separated from unreactivated portions in asimple manner. 6

The term clay as herein used refers to inorganic adsorbents in general,all of which possess silicates such as fullers earth, sub-bentonite's,

montmorillonites, acid-activated clays; silica gel, 10

ferric hydroxide gel, bauxite, aluminum hydroxide, magnesium hydroxide,etc.

I have discovered that if I treat a spent clay with liquid water at atemperature above about 300 F., the water substantially completelydisplaces the adsorbed matter, so. that the latter can easily beextracted with a suitable tar solvent. The quantity of water used in thetreatment must be sufiicient to have it distributed in the liquid statethroughout the mass of clay undergoing the treatment. If desired thehydrolytic treatment may be carried out in the presence of a tarsolvent. During the treatment a sufiicient pressure is maintained tokeep at least the water in the liquid phase and preferably both thewater and the tar solvent, if the latter is present.

I am aware that spent clays have been treated with'mineral acids attemperatures above their normal boiling points and under pressuresufficient to maintain them in the liquid phase. However, aside from thesevere corrosion difficulties of this process, mineral acids at theseelevated temperatures have strong leaching effects, which in the case ofsilicates not only cause removal of metal components, thereby 5effecting a breakdown of the silicates, but also colloidally dissolveconsiderable quantities of silicic acid. Both'of these eifects stronglytend to lower the adsorption power of the clay. Moreover, mineral acidscannot be used to reactivate spent basic adsorbe r:, such as bauxite,ferric hydroxide, etc., wLr--. adsorbents readily respond to mytreatment with water as the displacing agent.

An upper temperature limit formy pressure hydrolytic treatment is set bythe decomposition of the clay itself. It has been noted that some claysshow signs of decomposition beginning at about 500 F. and possiblyslightly lower, while other clays are stable at considerably highertemperatures up to about '700 F. and perhaps higher. Whether thisdecomposition is a dehydration, resulting in a loss of active hydroxylradicals, or a hydrolysis which destroys the surface structure of theclay is at present-unknown. As far as the efficiency of reactivation isconcerned it is advantageous to operate at the highest temperature whichwill not result in a decomposition of the clay itself. If, moreover, thereactivation is carried out in the presence of a tar solvent, thepossible decomposition of the latter must also be taken intoconsideration, 1. e., the temperature should. be low enough to avoidsuch decomposition which may result in the formation of absorbablepolymers from the products I of decomposition. Furthermore, theextremely developed at high temperatures make it desirable to shift theoperating temperatures toward the lower efiective limits. In general,therefore, I prefer to carry out the hydrolysis between about 400 to 550F., under sufllcient pressure to maintain water and, if possible, thetar solvent if the latter is present, in the liquid state.

The time required to complete the reactivation varies somewhat withdifferent clays, type of adsorbed matter and the temperature of thetreatment. At 300 F. several hours may be required to achievesubstantial reactivation, whereas at 550 F. the reactivation may becomplete in less than five minutes. a

While it is not essential that the tar solvent be present during thehydrolysis, its presence is advantageous, for it is easier to wash thereactivated clay clean of the liberated tar, if the high pressureslatter is dissolved as soon as released by the clay.

Moreover, a peculiar separation of reactivated and umeactivated portionsof the clay takes place in the presence of the tar solvent. Usually arelatively small portion of the clay, which portion may vary from about1 to 20%, fails to respond {to the reactivation treatment. This in thetar solvent or accumulates as 'an intermediate layer at the interface ofthe water and the tar solvent, when the two liquids are allowed tosegregate after the completion of the hydrolysis, while the reactivatedportion of the clay sinks to the bottom of the water layer. Theunreactivated portion may be discarded or be further reactivated by asimilar hydrolytic treatmentpreferably at a somewhat higher temperature,or it may be added to untreated spent clay and be retreated incombination therewith.

Organic solvents whiqh possess good tar dissolving properties, which aresubstantially nonmiscible with water and which arerelatively volatile,i. e., normally boil below about 650 F. and preferably below 550" F.,are in general suitable for my process. Some solvents having therequired properties may, however, be excluded because they are unstableat the high temperatures and in the presence of clay and water. Forinstance,- chlorinated hydrocarbons, while having favorable solventproperties, tend to hydrolyze and liberate hydrochloric acid withconsequent corrosion and other difficulties. Of particular utility arethe normally liquid aromatic hydrocarbons of relatively low boilingtemperatures' as benzene, toluene, xylenes, other alkylated benzenes,tetrahydronaphthalene, al-

' kylated naphthalenes, aromatic mineral oil fractions as crackingrecycle stocks, particularly the tracted bright stock with 8% lowerboiling portions thereof, cracked naphtha, dehydrogenated naphthenicnaphtha, extracts from kerosene obtained with selective solvents fornon-paraffinic hydrocarbons or their products of dehydrogenation etc.;normally liquid, saturated i. e., non-olefinic, oxyhydrocarbons of 5 to10 carbon atoms containing not more than one oxygenated radical of thegroup of alkoxy and carbonyl radicals, examples being monoalcohols suchas amylalcohol, benzyl-alcohol; mono-ethers as dipropylether, anisol;simple ketones as methyltpropyl ketones; fatty acids as valeric acid,etc.

The use of parafnnic hydrocarbons as pentaue, hexane, parafiinicgasoline distillate, etc., having poor tar solvent properties'is lessdesirable and results in incomplete reactivation.

Some of the solvents which are suitable in my process, if used bythemselves have the ability to act as displacing agents; yet in thepresence of water under the conditions of my treatment,

water having the greater ailinity to clays than even the most polarneutral or acidic organic substances, immediately displaces tar solventsthat might be adsorbed. Thus it is seen that in eifect water is the soledisplacing agent in my process.

Besides containing adsorbed'matter, spent clay usually containsrelatively large quantities of occluded oil. It is not essential thatthis oil be removed prior to the hydrolytic treatment. If this oil hasgood tar solvent properties it may be of advantage to leave it there. Inmost instances, it out with one of the suitable solvents hereinbeforedescribed, or with a low boiling hydrocarbon as light naphtha, propane,butane, pentane, hexane, etc., to recover the oil. The clay which nowcontains light solvent is then subjected to the pressure hydrolysis withwater, preferably in the presence of added amounts of tar solvent.

After completion of the hydrolysis the mixture is cooled, and thepressure is released. If a tar solvent is present, the liquids areallowed to segregate and are separated. The aqueous layer contains thereactivated clay which is most easily separated by filtration. If no tarsolvent was present during the hydrolysis, the filtered cake must bewashed with a suitable tar solvent to remove adhering tar, and retainedsolvent is expelled preferably by steaming, or if the solvent isrelatively high boiling, by washing with a light hydrocarbon distillatefollowed by steaming. After this, the clay is ready for reuse.

The following examples serve to illustrate my process.

An acid activated clay of the sub-bentonite type (Filtrol) used in thetreatment of solvent extracted bright stocks was treated in a closedautoclave with equal volumes of water and methyl isobutyl ketone at 500F. for twenty minutes. The mixture was then cooled and allowed toseparate. About 5% of the clay remained suspended in the ketone whilethe reactivated clay settled out. The two liquids were separated andflltered separately. The clay recovered from the settled portion and theaqueous layer was steamed and tested for decolorizing efliciency incomparison with fresh clay and clay reactivated by extraction withmethyl isopropyl ketone alone. The decolorizing test consisted ofheating solvent exof the clay to be however, it is more desirable towash- 2,162,202 r p 3 tested to 520 F. and filtering. The following inthe presence of an added aromatic hydrocarcomparative results wereobtained: bon oil capable of dissolving tar which oil is slstant todecomposition under conditions of the Clay eelelr a es treatment, at a.temperature above 300 F. but 7 below that at which the clay itselfismaterially Fresh Dark 5 changed, under a pressure suflicient tomaintain rieshftnthslsii'io's'ifi iIIIIIIIIII"""IIIII water in theliquid State. gg z ggsgg22322 2 Dark 8 2. In the process of reactivatingspent decolor- Twice pressure reactivated at 500 F izmg y contamingtarry adsorbed matter, the ggzg g a g gff i zE at steps of treating theclay with a suflicient amount Twice solvent extractedIIIZZY I of Wateras e Sole displacing agent for the tarry Three times Solvent extmcteiadsorbed matter, in the presence of an added aromatic hydrocarbon oilcapable of dissolving tar T nature of the tar solvent is of some whichoil substantially immiscible with-water p n a is h wn low. Spent claywas presand resistant to decomposition under the condisur hydrolyzed at520 F. for twenty minutes in tions of the treatment, at a temperatureabove h p n f different r v n B i 300 F. but below that at which theclay'itself is stock was decolorized as described before with thematerially h d, d r a, pressure sumoien't to clays so reactivated,giving the following results mai t in te in the liquid stat and toproduce two liquid layers, an upper layer consisting pre- NQQGaQ a A. s.'r. M. dominantly of said oil containing dissolved tar f g fig andunreactivated clay in suspension, and a lower Extract distillate 8Mid-Qontinent g asoil" 7 3. In the process of reactivating spentdecolor- Crackmg cycle dlstuate g izing clay containing tarry adsorbedmatter, the

M m 1' 'lkt e y 150mm 8 one steps of treating the clay with a suflicientamount of water as the sole displacing agent for the tarry adsorbedmatter, in the presence of an added aromatic hydrocarbon oil capable ofdissolving tar which oil is substantially immiscible with water andresistant to decomposition under the conditionsof the treatment, at atemperature above 300 F. but below that atwhich the clay itself ismaterially changed, under a pressure suflicient to maintain water in theliquid state, cooling the mixture and allowing it to segregate, to formtwo liquid layers, an upper layer consist- In another series ofexperiments, the colors of the decolorizing test oils were determined bya method more accurate than the A. S. T. M. method. The decolorizingeificiencies of various clays were determined in per cent of the amountof color removed by fresh clay. All the decolorizing treatments werecarried out with 8% by weight of clay at 520 F. The followingdecolorization efiiciencies of various clays were found:

any T8! olven 333353351,"; ing re ominantly; of said oil containingdissolved tar and unreacted clayin suspension, and a lower water-layercontaining the reactivated clay, and

:h separating the layers. siistm imitated "it nitrates-satin? 92 Theprocess of claim 2 m which the unrek d 86 activated clay is separatedfrom the aromatic oil 0 "7" 3 me e and is further treated with liquidwater at a temperature higher than that of the first treatment.

The ratio of Water to tar Solvent in the above 5. The process of claim 1in which the aromatic.

oil is a cracking recycle stock boiling below 650 I 1 m invention; 6.The process of claim 1 in which the aromatic L 3 i g of reactivatingspent decoloh oil is a kerosene extract obtained by extraction izingclay containing tarry adsorbed matter, the of kerosene with a selectivesolvent for nonstep of treating the clay with water as the sole parammchydmcarbons- FUCHS displacing agent for the tarryadsorbed matter, GEORGEHUGO examples was about 1:1.

